Production of cured epoxide resins



, ing of the aforementioned 'anhydrides under heat can United States Patent 2,884,406 PRODUCTION OF CURED EPOXIDE RESINS Richard Wegler and Giinter Frank, Leverkusen, Germany,

assignors to Farbenfabriken Bayer Aktiengesellschaft, Leverkusen, Germany, a corporation of Germany No Drawing. Application September 11, 1956 Serial No. 609,086 Claims priority, application Germany October 4, 1955 6 Claims. (Cl. 260-47) 1 This invention relates to the production of cured epoxide resins.

It is known that non-basic organic compounds containing more than one epoxy radical per molecule such as polyepoxides of dihydric and polyhydric phenols (especially of 4,4-dihydroxydiphenyl-dimethylmethane and derivatives thereof), of dihydric and polyhydric alcohols (for example glycols, glycerine and trimethylol propane),

furthermore glycol-bis-l,2-epoxy-4,7-methanoperhydroindane-S-ether, furthermore butadienedioxide, for example, can be converted into cross-linked plastics by heating for a relatively long time with cyclic acid anhydrides (for example phthalic anhydride, tetrahydro phthalic anhydride, hexahydrophthalic anhydride, maleic anhydride or succinic anhydride) or with polybasic acids (carboxylic acids, su'ch'as for example citric acid, tartaric acid, maleic acid, itaconic acid, succinic acid or adipic acid: sulphonic acids, such as for example benzene-disulphonic acid; in-

or'ganic acids, such as for example phosphoric acid).

The advantage of using cyclic acid anhydrides as compared with the acids mentioned above is that no hydroxyl groups are formed in the cross-linking (polyester formation) and that the anhydrides cross-link with polyepoxides completely without giving off volatile components (H 0). Such combinations are used in practice inter alia as casting resins, surfacing materials, lacquers, adhesives and electric insulating materials. As regards the constitution'and preparation of the non-basic polyepoxide compounds compare for instance United States patent specifications Nos. 2,324,483, 2,581,464, 2,642,412. As used herein the term non-basic denotes a polyepoxy-compound which contains neither a nitrogen containing group nor any other basic group.

A fact which is occasionally disadvantageous is that 'the curing times of such combinations are too long or the hardening temperatures, for example for molding masses, cold-hardening lacquers and casting resins for electrical purposes are too high. It is true that the curdiand polyepoxides with cyclic be accelerated by the addition of tertiary amines, but these amines have the disadvantage that they are volatile and are not incorporated into the polyesters which These are incorporated chemically into the resin molecule, but have the disadvantage that they bind some of the epoxide groups or carboxyl groups and thus modify the technical properties of the hardened products obtained.

It has now been found that, in the presence of basic diand polyepoxides, the reaction of non-basic diand poly epoxides with cyclic acid anhydrides or polybasic are formed. It is also known' that diarnines with primary and tertiary amino groups can be used as accelerators.

organic orinorganic acids is accelerated without the J aforementioned disadvantages, so that simultaneously the hardening times are shortened or the hardening temperature is lowered.

v Accelerators especially suitable forthe hardening are pyl, butyl or cyclohexyl radical,

,caustic alkali solution. N-di2,3-epoxypropyl aniline, N-di-2,3-epoxypropyl butyl- Patented Apr. 28, 19 59 organic nitrogen compounds which contain more than one epoxide radical. These epoxide radicals are preferably connected in the form of 2-3-epoxypropyl groups to one or several nitrogen atoms of the accelerator. Such compounds correspond to the general formulae:

in which R represents an aryl, alkyl, cycloalkyl, aralkyl or heterocyclic radical such as for example a phenyl, chlorophenyl, toluyl, anisyl, naphthyl, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, heptyl, stearyl or benzyl radical, R represents an alkyl or cycloalkyl radical, such as for example a methyl, ethyl, propyl, isopron represents zero or a whole number, preferably of 1-6, and X represents a divalent aliphatic or aromatic organic radical, such as for example an ethylene, a diethylene ether, phenylene, naphthylene, diphenylene or a diphenylene-ketone radical, or preferably a diphenylene-methane radical of the general formula in which R, and R represent hydrogen atoms or alkyl such as methyl, ethyl, propyl, cycloalkyl such as cyclohexyl such as benzyl radicals, it being possible for R and R to be the same or different and moreover to form part of a cycloaliphatic ring, and R and R represent hydrogen or halogen atoms or alkyl or alkoxy radicals.

A represents a divalent aromatic organic radical such as those designated with X. 7

Basic diepoxides of the general Formulae I and II are for example obtained according to US. application Serial No. 551,212 wherein free amines are reacted with epichlorhydrin to form the corresponding di-(hydroxychloropropyl)-amines and these are treated with aqueous Examples of such compounds are to 6 hours after being r, .'L& The basic dior polyepoxides can be added in any desired proportion to the non-basic diepoxides and polyepoxides. The cyclic acid anhydrides, the polybasic or- .ganic or inorganic acids or mixtures of said compounds which-are to be employed as hardening agents, should preferably be used in such an amount asis equivalent to the total .amount of basic and non-basic diepoxide or polyepoxide. actually used. Larger or smaller amounts .of acid anhydrides can however also be used for prehardening purposes.

As accelerators, the basic diepoxides and polyoxides are advantageously used in a proportion of 0.1% by weight, preferably 0.14%, calculated on the non-basic polyepoxide compounds to be hardened.

The reaction conditions for the production of plastics by reacting non-basic diepoxides or polyepoxides with cyclic acid anhydrides and/or polybasic organic or inorganic acids in the presence of basic diepoxides or polyepoxides depend on the state of aggregation of the basic and non-basic diepoxides or polyepoxides which are used. If these compounds are liquid, they are mixed and the hardening is carried out at elevated temperature after addition of the aforementioned acid anhydrides or organic or inorganic acids serving as hardening agents. If one epoxide compound is solid, the hardening reaction is carried out in the melt. The hardening temperatures in such cases are preferably between 80-150 C., although lower or higher temperatures may beused. taneously using different amounts of non-basic .di- 01'; polyepoxides, it is also possible additionally to influence the degree of cross-linking. On the other hand, not only can the catalytic effect be influenced by the basic diepoxides or'ipolyepoxides, but it can also be influenced by varying the degree of basicity of the basic diepoxides or polyepoxides.

The advantageous catalytic effect of the said basic diepoxides as compared with amines containing no epoxide,

is that the basic diepoxides are concurrently cross-linked and do not show any chain-breaking effect. Since the said pure diepoxides meet with cyclic anhydrides to produce plastics with excellent mechanical and electrical values, the proportion of the basic polyepoxides chosen can be as high as desired. In this way, it is possible to produce cold-hardening polyester-based lacquers with high-grade properties.

The following examples further illustrate the invention.

Example I The catalytic efiicacy of the basic diepoxides or polyepoxides is most clearly shown by comparison of the gelling times.

An epoxide resin is prepared by mixing 1 mol of 4.4- dihydroxydiphenylmethane with 2 mols of epichlorhydn'n. To this mixture there are slowly added at 80-100 C. an aqueous solution of sodium hydroxide in a quantity suflicient to bind the hydrochloric acid formed during the reaction between the aforementioned components. After the resin which is formed has reached the desired consistency, the resin is washed free from alkali and the water is removed in vacuum.

The resin thus obtained has an epoxide equivalent of 0.256 per 100 g. of resin. It gels at 120 C. after 5 /2 mixed with the equivalent amount of phthalic anhydride. By adding varying amounts of N-2,3-diepoxypropyl aniline, the gelling times were shortened as follows:

Epoxide N-diepoxy- Phthalic Gelling resin in g. propylanhytride time, aniline m g. m g. hours 10 0 1 3.8 about 2 10 0 4 4. 3 about 2 By *simul The N-diepoxy propyl aniline is prepared as follows:

A mixture of 400 g. of epichlorhydrin (4 mol=370 g.) and 400 cc. of methanol is heated to boiling point. 2 mols of aniline are then added dropwise over a period of 15 minutes and the solution boiled for 3 hours under reflux. The alcohol is then distilled off, 200 cc. of benzene are added, and 600 cc. of 44% sodium hydroxide solution are added dropwise at 2025 C. over a period of 30 minutes. The mixture is vigorously stirred for another three hours and then such an amount of water is added that all the precipitated sodium chloride re-dissolves. The layers are then separated. The benzene solution of the diepoxide is briefly dried with solid potassium hydroxide and distilled. The fraction having the boiling point :136-138 C. is the pure diepoxide, which is a light yellow highly mobile oil. Yield: 314-340 grams=76-82% of the theoretical.

Analysis for C H O N-Calculated: C, 70.24%; H, 7.31%; N, 6.84%;0, 15.61%. Found: C, 70.20%; H, 7.45%; N, 6.80%; O, 15.65%.

Example 2 Epoxide resin as in Example 1, N-di-2,3-epoxypropylpropylamine was used as catalyst. Hardening tempera- The N-di-2.3-epoxypropyl-propylamine is prepared :as follows:

59 grams of n-propylamine (1 mol) are added dropwise to 200 g. of epichlorhydrin (2 mols=185 grams) While stirring at 28-32 C. over a period of 30 minutes; for four hours. The mixture is cooled to 20 C., and 300 cc. of 44% sodium hydroxide solution are added dropwise over a period of 30 minutes at 20-25" C. The mixture is stirred for 3 hours and then diluted with about 300 cc. of water, whereupon all the sodium chloride precipitated re-dissolves. The resulting mixture is allowed to settle and the upper layer is separated off; this layer is shaken for a short time with cold 50% potassium hydroxide solution, and then the upper layer is separated and distilled under water jet vacuum (B.P. C.); by rectification, 122 g.=71% diepoxypropane propylamine (B.P. =1l3-115 C.) are obtained. The diepoxide is a crystal-clear highly mobile liquid which becomes slightly yellowish in color after standing for a relatively long period.

Analysis for C H O N-Calculated: C, 63.15%; H, Found: C, 62.75%; H, 10.00%; 0, 19.00%; .N, 8.1%

Example 3 Epoxide resin as in Example 1. Catalyst: 'NN'-di- 2.3-epoxypropyl-dimethylamino-diphenylmethane. Hardening temperature: 120 C.

The N.N-di-2.3-epoxypropyl-dimethylaminowdiphenylmethane is prepared as follows:

1582 g. (=7 mols) of 4.4'-di-(mono-methylamino)- diplienylmethane v The mixture is boiled and 1400 grams of epichlorhydrin A ture is stirred vigorously 1 precipitated sodium 1 liters); settlement is are separated. with solid potassium hydroxide and the benzene is distilled ofi. The last traces of solvent are removed under are dissolved in 1.4 liters of benzene.

are ded dropwise at the boiling point over a period .o, 22% hours while stirring. The mixture is heated for a' further 15 hours while stirring, cooled to 20 C.,

ture and such an obtained which is still liquid Yield: 2322 grams=98% of vacuum. A resin is and light brown in color. the theoretical.

Analysis for C, H N -Ca'lculated: c, 74.55%; H,

- Found: C, 74.40%; H,

7.69%;N, 8.28%; O, 9.46%. 7.91% N, 8.00%; O, 9.40%.

Example 4 lipiiiiide'resin as in Example 1. Catalyst: Bis-(N- diepoxypropylaminophenyl)-methane. Hardening temperature: 120 C.

E ride Catalyst Phthalle Gelllng re in g in g. anhydrlde times in g.

10 3. 8 6 hours. 10 0. 1 8. 8 1 hour. 10 0. 4. 5 37 minutes. 1. 0 5 26 minutes.

The catalyst is obtained as follows:

396 g. (2 mols) of 4,4-diamino-diphenylmethane are dissolved in 500 ml. of methanol. To the boiling solution there are added drop by drop 800 g. of epichlorhydrin, whereafter the mixture is refluxed for 10 hours. The methanol is distilled off and 1 litre of benzene is added. To this solution there are added 1.2 litres of a 40% aqueous solution of NaOH at -25 C. within a period of 1-S hours. The mixture is kept stirring for 15 hours, thereafter 2 litres of water are added, the layer of henzene is isolated and washed with sodium chloride solution. The benzene is partially distilled oil until clear water free solution is obtained. This is filtered and the rest of the solvent is distilled oil". There are obtained 823 g. of a yellow, viscous resin with an epoxide equivalence of 150- 170. In analogous manner there may be obtained and used accelerators of the following formulae:

0 o O ACE-CH1 CH; CHrC--CH! l o N I N\ OQCH-Gg CH CHr-CH--CH:

0 0 (Ha-$343K: CHa-fl- HI Example 5 Epoxide compound as in Example 1. Hardener:'hexa hydrophthalic anhydride. Catalyst: N-di-2.3-epoxypropyl-propylamine. Hardening temperature: C.

Epoxlde Catalyst Hardener Gelling resin in g. in g. in g. times 10 7. 4 6 hours. 10 0. 1 7. 4 8 minutes. 10 0. 5 8 3 minutes. 10 1.0 8. 6 1 minute.

Example 6 Epoxide compound as in Example 1. Hardener: hexahydrophthalic anhydride. Catalyst: N,N'-tetra-2.3 -epoxypropylaminodiphenyl methane. Hardening temperature:

Epoxlde Catalyst Hardener Gelling times resining. ing. lug.

10 7. 4 6 hours. 10 0. 1 7. 4 124 minutes. 10 0. 5 8 77 minutes. 10 l 8. 6 37 minutes.

What we claim is:

1. In a process of curing a non-basic polyglycidyl ether of a compound selected from the group consisting of a polyhydric alcohol and a polyhydric phenol at elevated temperature by means of a curing amount of a curing compound selected from the group consisting of a cyclic acid anhydride, a polybasic organic acid, and an inorganic acid, the improvement which comprises curing said polyglycidyl ether in admixture with said curing compound and in admixture with 0.1-5 by weight, based on the polyglycidyl ether, of an organic tertiary amine catalyst containing at least one tertiary nitrogen atom to which is bound at least one 2,3-epoxypropy1 group, at least two 2,3-epoxypropyl groups being present in said catalyst, said catalyst containing no other groups reactive with polyglycidyl ethers and acid anhydrides.

2. The process of claim 1, wherein the tertiary amine is selected from the group of compounds of the formulae:

in which R represents a radical selected from the group consisting of aryl, alkyl and aralkyl radicals;

in which A represents a divalent aromatic radical;

in which R represents a radical selected from the group -1'Q0nsistingof- 1alkyl and ,cycloa'lkyl radicals, n represents J 16,,:&nd Xrepresents agdivalent aliphatic or aromatic .organic; radical, including a diphenylene methaneradical of the general formula in which k xand R each represent hydrogen atoms, alkyl, cycloalkyl, 'andzaralkylradicals,R and Rg-together form part ofacycloaliphatic ring, and- R and-R -represent hydrogen, halogen, alkyl, and alkoxy radicals.

3. Resins produced by ithe process of claim 1.

4. A composition of matter comprising l) a non-basic -polyg lycidyl cther of a-compound selected from the group consisting of a polyhydric alcohol and a -polyhydric "phenol,(-2) a'compound selectedirom-the group consist ing of cyclic acid anhydride, a polybasic organic acid, and an inorganic acid, and (3) a tertiary amine catalyst containing at least one tertiary nitrogen atom to which is bound at least one2;3-epoxypropyl group, at least two 2,3- epoxyprqpyl groups being present in said amine.

prolyglycidyl ether in admixturevwith .5113 V f5. 'Composition .of claim 4 whereinwsaid tertiary min is used in a proportiono'f Ollfto 5% by weight based on the weight of said polyglycidyl ether.

6. In a process of curing ,a non-basic polyglyci'clyl ether of ,a compound selected from the group consisting .of a polyhydric alcohol and a polyhydricphenol at'ejlevated temperatures by means of'a curing amount ofja curing compound selected from the group consisting ,ofa cyclic acid anhydride, a polybas'ic organic acid, and an inorganic acid, the improvement which comprises curing the said cur ng compound and in admixture with 0.1 5% by weightbaseadn the weight of the non-basic polyglyci'dyl ether, of an epoxyamine catalyst sselectedfrom the group consisting .cif N 2,3 ii p xy w pyl an i NgN' ,di -,2;3-

p pyl propylam'ine and N,N'

tetra 2,3 eponypropylamina-diphenylmethane.

References Cited inithe file of this -patent UNITED STATES PATENTS 2,730,531 Payne et a1 Jan.v 10, ,1956 

1. IN A PROCESS OF CURING A NON-BASIC POLYGLYCIDYL ETHER OF A COMPOUND SELECTED FROM THE GROUP CONSISTING OF A POLYHYDRIC ALCOHOL AND A POLYHYDRIC PHENOL AT ELEVATED TEMPERATURE BY MEANS OF A CURING AMOUNT OF A CURING COMPOUND SELECTED FROM THE GROUP CONSISTING OF A CYCLIC ACID ANHYDRIDE, A POLYBASIC ORGANIC ACID, AND AN INORGANIC ACID, THE IMPROVEMENT WHICH COMPRISES CURING SAID POLYGLYCIDYL ETHER IN ADMIXTURE WITH SAID CURING COMPOUND AND IN ADMIXTURE WITH 0.1-5% BY WEIGHT, BASED ONO THE POLYGLYCIDYL ETHER , OF AN ORGANIC TERTIARY AMINE CATALYST CONTAINING AT LEAST ONE TERTIARY NITROGEN ATOM TO WHICH IS BOUND AT LEAST ONE 2,3-EPOXYPROPYL GROUP, AT LEAST TWO 2.3-EPOXYPROPYL GROUPS BEING PRESENT IN SAID CATALYST SAID CATALYST CONTAINING NO OTHER GROUPS REACTIVE WITH POLYGLYCIDYL ETHERS AND ACID ANHYDRIDED. 